Random House, the largest trade publisher in the world, reported revenues for the first six months of the year of 818 million euros ($995 million), up 9.5% from a year ago, and earnings almost three times higher at 31 million euros (nearly $38 million).

Parent company Bertelsmann – where sales rose 3.3% overall to 8.14 billion euros ($9.75 billion) and profits rose compared to a large write-down last year – underscored Random’s “especially strong sales and profits in the U.K. and Australia” and an “impressive increase in its operating results” in Germany, along with “an excellent start” for its joint ventures in Asia, “especially in Korea.”

Reading between the lines, that omits any praise for the North America book publishing unit, which generates somewhere around half of the division’s revenues. This helps explain why Random House chief executive Peter Olson’s celebratory letter to employees balanced “very good news to share about our excellent financial performance” with an overarching caution.

Mr. Olson remarked on “the uncertainties over what lies ahead for our business these next few months.” From his vantage point, “Any real upturn at book retail in 2004 has been largely unsustained, and while we’ve had some major new breakout hits these past two months, generally consumers were more frugal in their book purchases this summer than they were in the spring.”

Indeed Random House’s performance in America owes much to the unexpected continuing success of hit books originally published last year such as “The Da Vinci Code” and “Eragon” as it does to new books like Bill Clinton’s “My Life.” For a few years, the Random House unit has shown little or no meaningful year-to-year growth in sales, even as competitors like Harper-Collins have grown steadily.